In Quiver Function Error: " index must be a positive integer or logical."

2013 8 13
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Hey,
I get the error
??? Attempted to access quiver(2.76604,2.17365,-0.123257,0.81116); index must be a positive integer or logical.
and can't imagine why, because if I type quiver(2.76604,2.17365,-0.123257,0.81116) in the Command Window it works well.
Here is the Code:
for k=1:n
for l=1:n
if E(k,l) >= 1
x1=2+cos(2*pi/n*k); x2=2+cos(2*pi/n*l); y1=2+sin(2*pi/n*k); y2=2+sin(2*pi/n*l);
u=y1-x1; v=y2-x2;
quiver(x1,x2,u,v);%,'Color',color,'LineWidth',2);
end
end
end
with n=length(E) and E(i,j) = 1 if there excists an arrow between i and j
Thank You Daniel

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David Sanchez
David Sanchez 2013-8-13
I run the following code and it worked for me:
n=3;
for k=1:n
for l=1:n
x1=2+cos(2*pi/n*k);
x2=2+cos(2*pi/n*l);
y1=2+sin(2*pi/n*k);
y2=2+sin(2*pi/n*l);
u=y1-x1;
v=y2-x2;
quiver(x1,x2,u,v);
end
end
Is the code you presented the one that yields the error?
Daniel
Daniel 2013-8-13
Hmm this is weird because if I run exactly your modification of the code I get the error:
??? Attempted to access quiver(1.5,1.5,1.36603,1.36603); index must be a positive integer or logical.
Error in paintgraph at 23
quiver(x1,x2,u,v);
I can't imagine why. Yes the code I presented yields the error.
Daniel
Daniel 2013-8-13
Got the solution. I accidantly set quiver=1 earlier.
Thank you very much.

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